The following disclosure is based on German Utility Model Application No. 200 19 881.5, filed on Nov. 23, 2000, which is incorporated into this application by reference.
The invention relates to a face seal device for use with components rotating at a high rotational speed.
The invention relates, in particular, to a face seal device for use with turbine engines e.g. in aircraft construction. In applications of this type, it is not permissible to use pairings of ceramic material for the face seal rings although these would be preferable, basically, because of their high wear-resistance properties. Consequently, it is pairings of a steel material that receive prime consideration for the rotary face seal ring, whilst the static face seal ring may consist of a carbon material. At the high rotational speeds involved in such types of applications, and despite the absence of direct contact, the face seal rings may experience a heating effect due to the friction between the cooperating face seal rings and the gaseous or liquid medium in the sealing clearance (molecular friction) to such an extent as to lead to thermally induced distortions or deformations, especially in the rotating face seal ring, whence the geometry of the sealing clearance could be adversely affected. In particular, the sealing clearance may open in the manner of a wedge (formation of a so-called V-gap) thereby resulting in considerably higher leakages.
One object of the invention is to provide an improved face seal device suitable for high rotational speeds while having minimized leakage. Another object of the invention is to provide a face seal device having a rotary face seal ring which, while it can be made of any suitable material including materials permissible in aircraft construction, avoids detrimental effects in regard to the geometry of the sealing clearance caused by thermally induced distortions of the rotary face seal ring at high rotational speeds.
These and other objects are solved by a face seal device according to the present invention for use with components rotating at a high rotational speed. According to one formulation of the invention, such a face seal device includes a non-rotating face seal ring and a rotary face seal ring, wherein the rotary face seal ring is formed for mounting in a loose fit on the rotary component for common rotation therewith. The rotary face seal ring includes a sealing face which, in operation, is essentially radially aligned for cooperation with an opposite sealing face of the non-rotating face seal ring. The rotary face seal ring is formed from of least two sub-portions including a base portion and an extension portion. The extension portion creates an additional mass and has an areal center of gravity axially spaced from the areal center of gravity of the base portion such that the axial spacing z between the areal centers of gravity and the mass of the extension portion satisfy the following equation:             m      *      z        =          k      *              10                  -          2                    *      Δ      ⁢              xe2x80x83            ⁢      T      *                                    (                          D              -              d                        )                    *                      b            2                                    r          *                      n            2                              *      q            k    =          α      *      E      
where
k=xcex1*E
and where q is in a range between 0.5 and 2.0, preferably between 0.7 and 1.5, and most preferably between 0.8 and 1.3. For the meaning of the symbols used in this equation, reference is made to the following description of a preferred embodiment of the invention.
The at least two sub-portions, which together form the rotary face sealing ring are preferably formed as a single piece or, at least, are rigidly connected with each other. The axial spacing between the center of gravity of the extension portion and that of the base portion is arranged to be such that the rotary face seal ring will be subjected to a specifically oriented torque in correspondence with the spacing between the centers of gravity and the centrifugal forces effective on the extension portion. A thermally induced deformation of the rotary face seal ring is thereby effectively countered and a compensating effect for a change in the geometry of the sealing clearance caused by such a deformation is obtained, so that the desired geometry of the sealing clearance will be maintained even at high rotating speeds even if the rotary face seal ring consists of a steel material which is subjected to incomparably greater thermal distortion than ceramic material due to the different thermal conductivity and co-efficient of thermal expansion of these materials.